The purpose of this project is to provide consultation on statistical and epidemiological methodology in the design, interpretation, and evaluation of clinical trials of diagnosis, treatment, and prevention of cancer, and other studies requiring this kind of expertise. For some studies the Section provides full statistical support, including development of detailed study plans; assistance in the design of appropriate study forms; supervision of randomization (for trials); collection, processing, and editing of data; performance of interim analyses during the progress of the study; preparation of progress reports; final analysis of study data; and collaboration in the preparation of scientific papers. During the past year the Section has continued to collaborate extensively on the design and implementation of the Community Intervention Trial for Smoking Cessation. Key activities during this year were analysis of data from past surveys for presentation to the Policy Advisory Committee, designing the final cohort and cross-sectional surveys to be completed in 1993, and design of the cotinine validation study to follow the final cohort survey. The Section has continued to provide full statistical support for the randomized clinical trials of multimodality treatment conducted by the Brain Tumor Cooperative Group. Other important activities this past year include consulting on design issues in largescale randomized prevention trials relating to breast cancer and prostate cancer; providing statistical consultation for the 5-A-Day Program; characterizing the American diet using data from large national surveys, and analyzing the relation of dietary patterns to demographic variables; analyses of data from feeding studies; and collaborating on a study, using a three-arm randomized design, of the adoption and use of the NCI Primary Care Nutrition Guide.